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The ABC's of Pest Control: Allergens, Baits, and Cockroaches

Cockroach infestations can get out of hand quickly in multifamily housing. Best practices and treatments can turn things around to help maintain control. Watch this StopPests in Housing for a webinar on reducing asthma triggers in housing with effective cockroach control. You'll hear from Dr. Coby Schal, Ph.D, Department of Entomology, North Carolina State University. He will speak about his research on effective baiting techniques, and ineffective controls like total release foggers (bug bombs). Cockroach allergens have been linked to the development and increase in symptoms of allergies and asthma in cockroach sensitive individuals. You'll learn how allergen levels can be significantly reduced with cockroach control alone, the most effective approach being gel bait treatments. Dr. Schal's work shows how an integrated pest management (IPM) approach with intensive, targeted cockroach control can lead to both dramatic reductions in cockroaches and clinically significant declines in cockroach allergens. You'll get the information you need to advocate for and implement an IPM approach to cockroach control. This webinar is for all housing professionals and partner agencies who want to make housing safer and healthier for those that live and work there.

Questions and Answers from the live webinar

If you have any remaining questions send a message to stoppests@cornell.edu

Are insect growth regulators effective at controlling cockroaches?

Insect growth regulators (IGRs) are an effective control but they are only one tool. They are usually formulated as a spray but shouldn't be used side-by-side with baits. They can deter a cockroach from eating the bait. Use the spray in one place and baits in another. Don’t spray products over the baits.

Are boric acid products effective and are they toxic to humans?

Boric acid dust is ingested by the cockroach after they walk through it and groom themselves. Boric acid dust is still used but it is limited as to where it can be applied - out of reach of people. Regarding toxicity risk with boric acid: Toxicity to boric acid is relatively low in mammals. You do not need to apply gobs. Use a light dusting only where it will not be visible – wall voids, closet voids, behind cabinets only. It takes massive doses to attain boric acid toxicity in humans. Baits with boric acid are not as effective as other baits because cockroaches tend to avoid them due to the strong taste.

Are desiccant dusts effective?

Silica gel is a desiccant - it is not ingested. Again, to be used only in places where it cannot be reached. You can put it there and leave it, it does not need to be refreshed. A good use of silica gel is application during construction.

How often should baits be rotated?

There is no data driven answer to this yet.

Should you use different baits concurrently or sequentially?

Do the taste test and see if the cockroaches like one bait over another. Then do it again. If they are still eating the preferred bait then no need to rotate. Dr. Schal prefers bait rotation rather than offering more than one type at a time.

How often should inspection and monitoring take place between bait placements. How long do they take to work?

Depends on the population, the larger the population the more bait will need to be applied. If you under apply then you'll know when you come back in a few days and all the bait is gone. Return at two week intervals and maybe more frequently for a heavy infestation. Are you knocking the population down? If you have a massive population, check again in two weeks, to make sure they are taking the baits. Or maybe you need to try another bait. Once the population goes down you can wait longer and longer times between inspection and bait application.

How long is the reproduction cycle of the German cockroach?

3 weeks carrying egg case and then babies hatch. Takes 6 weeks for those babies to become adults.

Any product recommendations?

Look at active ingredients rather than the product name and rotate active ingredients. Always use gel bait or bait station formulations to start with in situations with people and pets but keep in mind there are some circumstances which may need a spray application. Advion, Avert, MaxForce and Vendetta are a few. It's important to watch for resistance. All contain different active ingredients and are effective but we're starting to see resistance to all. It's important to test them. Put a small amount out. Don't buy cases of a product. Buy a small amount and make sure it kills your cockroaches first. Put a small amount out and see if the cockroaches eat it. Bait products with boric acid are less effective.

How do you know when an infestation is eradicated?

Two ways: Visual inspection and monitors (roach motels). With visual inspection use a can of compressed air to flush them out of hiding. With roach motels place a small amount of bait in the center to attract them. Put 6 monitors/roach motels in the kitchen in places where they hide. If after 2-3 consecutive inspections you see none, you probably have eliminated the population.

Any new developments in biocontrol agents or repellants?

The most commonly investigated biocontrol for cockroaches are fungal formulations (Ecopath is an example), but there is little or no efficacy in the field. These products tend to work well in the lab setting but not in the dry environment of a home. The short answer is no new developments. Research is happening but so far nothing that compares to baits. As for repellants, they work in lab but not in homes or apartments. You couldn't possibly apply enough to protect a home. Cockroaches, like bed bugs, will walk over repellant to get to food if they are hungry enough. What's available on market now is not even close to competing with baits for control. I would caution the use of repellants they can contaminate baits and cause the cockroaches to avoid baits. Essential oils are highly volatile and can settle on baits making the baits unattractive to the cockroaches.

How long are baits effective after they have dried?

Very likely not effective once they are completely dried out. They stay effective for a while because they have a high water content and cockroaches need water as well as nutrients found in the baits. They are most effective in the first 24 hours but there is a massive loss of water and continuous evaporation of water for about a month. It's best to remove dry bait with screw driver and apply new bait after it dries completely.

Why do you prefer sequential rotation of baits not multiple baits at once?

the theory is that numerous baits all at once will overwhelm the cockroaches but when you are using different placements of different baits you are not overwhelming the population with different baits, individuals typically find and eat one type. The risk of this all at once application is you may be selecting for resistance of all the active ingredients at once. So using one bait then another you will delay the resistance to one active ingredient. There’s no data to support either one of these approaches. Cockroaches have a high likelihood of developing resistance because they live all year round and a continuously growing population with 8 generation per year selects for resistance.

Send more questions to stoppests@cornell.edu

The Northeastern IPM Center receives support from the U.S. Department of Housing and Urban Development's Office of Healthy Homes and Lead Hazard Control through USDA-NIFA to facilitate this program. The materials contained herein present a research-based, balanced, and objective approach to pest management in affordable housing and are intended to be used in their entirety. Any nonobjective or partial use of the materials is not recommended. Products, vendors, or commercial services mentioned or pictured in the trainings or presentations are for illustrative purposes only and are not meant to be endorsements. Last update: March 8, 2017.